Now I tend to consider myself fairly well versed in computer hardware, but I figure I'll get some opinions.

My brother is enrolled in an Architecture Technologist program at college and as such has to design various buildings in AutoCAD Architecture. Now he's reached a point where he has to do renderings in 3D too, which apparently runs too slow and makes it seemingly freeze, but it eventually completes.

Would buying a Quadro/FireGL video card assist in this do you think? Or should I look more at the CPU?

Right now he has the following (my old system):

Intel X3350 (aka Q9450)

Maximus Formula X38

8GB DDR2-1066

HD5870

Seagate 7200.12 500GB

Conceivably, I could give him my current system of an i7 920 and 12GB of RAM and get myself a shiny new LGA2011, but I don't know if the CPU/platform would show much benefit.

Well if you can pair a Quadro with 920 rig, I think it will make a difference. However, may be you should repost it under AutoCAD's own forum. I wonder how much work can be off loaded to the GPU and would a Quadro be bottlenecked by an older platform such as the C2Q.

It just seems there's mixed opinions on Quadro's true benefits. They're technically much slower cards compared to GeForce, and they cost an insane amount. I can't see anyone agreeing to dropping $1k on a Quadro. He can just suck it up and live with the slowness

Resource wise, everything seems well below what I would have expected. Nothing is running 100%, so I'm not sure why it basically lags out (Windows actually says Not Responding) but it does eventually finish.